In this proposal we request partial support for the Fifteenth Biennial Gordon Research Conference on Mammary Gland Biology to be held at New England College, Henneker, New Hampshire, June 6-11, 1999. This highly successful and well attended conference is designed to bring together scientists from divergent scientific disciplines who share an interest in the mammary gland. The program has been selected to satisfy the multidisciplinary composition of the audience. The scheduled sessions include: Overview: setting the stage with questions; Prepubertal and pubertal regulation of mammary epithelial and stromal growth and development; Receptor mechanisms in steroid hormone and growth factor action; Cell cycle regulation in mammary development and tumorigenesis; Enzymes of milk synthesis: regulation and function; Specific role of the stroma in development and tumorigenesis; Adaptations of lipid metabolism to lactation; The EGF family of receptors and ligands in mammary development and tumorigenesis; and Signaling proteins in normal mammary development and cancer. At least one plenary speaker per session has not yet been chosen to allow room for speakers with new findings in this fast-moving field. Sixteen young investigators will be invited to present their work in poster discussion sessions that will end each morning session. Workshops on Experimental Manipulation of the Mammary Gland and on Expression arrays in the Study of Mammary Biology will be held in the late afternoon. All conferees will be invited to present posters. Conference presentations and discussions will not be published or cited, encouraging conferees to present new ideas and information to receptive peers. The success of the Conference rests on its informal atmosphere structured to facilitate multidisciplinary interaction. Most topics relate to the themes of mammary development, the basis of mammary tumorigenesis and development and support of milk secretion. In addition, several speakers will bring the role of environmental estrogens into their discussions. For this reason we are requesting triple assignment to NICHD, NCI and NIEHS.